Preparatory to welding a pair of metal members such as plates, pipes, fittings, and the like to one another it is necessary that the two members be so positioned relatively to one another that a proper weld may be achieved. In preparing the two members to be welded together, they usually are positioned adjacent one another with the edges to be welded confronting one another and spaced by a gap. It is rather uncommon for the confronting edges of the two members to match perfectly. On the contrary, more often than not the confronting edges are mismatched. That is, warpage of plates and out-of-roundness of pipes commonly will cause the surfaces of one member to be higher or lower than the corresponding surfaces of the other member, a condition which commonly is referred to as "high-low". To rectify a high-low condition, it is customary to use various kinds of shims, clamps, and the like so as to cause a low surface to be raised and a high surface to be lowered until they match or are in a desired relationship.
Among the tools heretofore proposed for rectifying high-low conditions are those disclosed in U.S. Pat. Nos. 4,175,734 and 4,175,735. These tools function well in those instances in which corresponding surfaces of two members are to be positioned in the same plane, but there are many instances in which such a relationship is not desired. For example, if a pipe having a relatively thick wall is to be welded to a pipe having a relatively thin wall, or if a relatively thick plate is to be welded to a relatively thin plate, then both corresponding surfaces of the two pipes or the two plates will not and cannot be coplanar.
When tools of the kind disclosed herein and in the two patents mentioned above are in use, it is not possible to effect a weld at the positions occupied by such tools. Thus, even though corresponding surfaces of two members may be coplanar at the position of the tool, a high-low condition may exist at a zone somewhat removed from a tool. If such high-low condition is to be remedied, therefore, the tool must be capable of effecting relative movement of the members at the location of the tool in an amount sufficient to overcome the high-low condition at such remote zone.
Other undesirable characteristics of some of the known tools are that they cannot be used on members of different shapes or in cases in which the tools cannot be disposed in a position that is either parallel or perpendicular to the members to be welded together. A tool constructed in accordance with the present invention, however, is sufficiently versatile to adapt to conditions in which parallelism or perpendicularity is not essential.
Another problem associated with tools of the kind heretofore in use is that it cannot always be determined when the high-low condition has been wholly rectified. A tool constructed in accordance with the present invention, however, may include a gauge which enables extremely accurate adjustment of the relative positions of the members to be obtained.